Why is my screen black but sound is perfect?

Hi,

Try shining a torch at an angle close to the screen when the TV is on and there is audio and check if you can detect any images at all. They will be very faint if they are there so trying this in a darkened room may help to see them if they are there.

If there are images then there is a backlight problem, either with the backlights or the power to the backlights from the power board. Further testing would be required to determine where the problem is.

If there are no images then combined with no backlighting (the screen would be lighter than when the TV is off if the backlights were on) it may be a mainboard problem or worse case a screen problem.